This invention relates to nail polishes, and particularly, to hypo-allergenic nail polishes.
The chief requirements of a satisfactory nail enamel are that it should apply easily, be well adherent, dry and harden quickly, be glossy, waterproof and suitably colored, wear well, be elastic, resist chipping, peeling and abrasion for a reasonable period of time, and be dermatologically innocuous.
In general, the main constituents of a nail enamel are the film former, a resin, colorants, plasticizer and solvents.
Nail lacquer formulations have depended on nitrocellulose as its main film-forming ingredient for many years. Derived from cellulose, it provides an unusual combination of properties of toughness, durability, solubility, and solvent release.
Nitrocellulose must be neutral, for free acid could damage the fingernail and destroy the colors of the polish. The most commonly used viscosity grades of nitrocellulose are so-called RS 1/4 sec., which has a high solids content, but poor wear resistance, RS 1/2 sec., which has better wear resistance and a reasonably high non-volatile content, and lastly, RS 5-6 sec. and RS 60-80 sec., which have higher viscosities than the RS 1/2 sec. grade.
The term RS refers to the RS brand of nitrocellulose with a nitrogen content of 11.2-12.8% with solubility in esters, ketones and glycol ethers manufactured by Hercules, Inc. The terms 1/4 sec., 1/2 sec., 5-6 sec., etc. represent viscosity and refer to the time it takes for a ball to fall to a given depth in the material.
Nitrocellulose is supplied in 70% concentrations, wet with 30% ethyl or isopropyl alcohol. Fingernail polish grade nitrocellulose has a low moisture content. Resins are used in nitrocellulose compositions to improve their depth, gloss and adhesion. The most widely used modifying resin in nail enamel is the toluenesulfonamide/formaldehyde resin which provides excellent depth, gloss, flow and adhesion as well as good resistant films. Addition of this resin and others permits an increase in solids content without appreciably increasing lacquer viscosity. Nail enamels, using a minimum of coats, are more easily attained.
The solvent combinations used in nail lacquer technology usually consists of the alcohol which is used to wet the nitrocellulose, together with an active solvent such as butyl acetate and an aromatic hydrocarbon diluent such as toluene. Additionally, solvents used are diluents. Diluents are organic solvents that are miscible with the nitrocellulose solvents, but are not themselves solvents for nitrocellulose. They are used to reduce the cost of formulation and help to lower and stabilize the viscosity of the enamels. Alcohols, aromatic hydrocarbons and aliphatic hydrocarbons are the classes of diluents used. Ethyl (78.degree. C.), isopropyl (82.3.degree. C.), and butyl alcohol (118.degree. C.) are the most efficient.
Most modern nail enamel formulations use a combination of camphor and another plasticizer. No one plasticizer possesses all the desirable properties necessary to obtain permanent extensibility and flexibility in the resulting films. Commonly used solvent-type plasticizers are dibutyl phthalate (bp 340.degree. C.), dioctyl phthalate, diphenyl phthalate, camphor, dibutoxy ethyl phthalate, tricresyl phosphate (241.degree.-255.degree. C.), triphenyl phosphate and citrate plasticizers.
Colorants for nail enamel are usually confined to the non-bleeding in lacquer solvents. The most widely used pigments in opaque enamels are red organic pigments, D & C Red #6, #7, #9, #10, #30, #33, and #34 Lakes, D & C Yellow #5 Lakes, titanium dioxide, iron oxides used to produce brown and tan shades and iron black and iron blue. Basic Violet #1 and #3, D & C Red #17, D & C Violet #2 and D & C Red #19 dyes are the most widely used soluble dyes for transparent systems. Pigments with relatively high specific gravities such as titanium dioxide and the iron oxides are most widely used in "creme" shades and most responsible for pigment settling problems.
An example of one formulation in percentages by weight of the total composition (w/w%) is:
______________________________________ W/W % ______________________________________ Nitrocellulose RS 1/2 sec.(dry) 15.00 film former Santolite resin (1) 12.00 resin Dibutyl phthalate 3.00 plasticizer Butyl Acetate 31.50 solvent Ethyl Acetate 9.00 solvent (to speed dry) Ethyl Alcohol 6.40 diluent-(coupling agent) Butyl Alcohol 1.10 diluent-(coupling agent) Toluene 21.00 diluent Colorant 1.00 100.00 ______________________________________
Reports of allergy due to nail polish usage have been documented and attributed to the sensitization effects of resins such as the arylsulfonamide/formaldehyde resins.
Attempts have been made to overcome this deficiency by substituting natural resins and polyesters as nitrocellulose modifiers in the manufacture of nail polishes. However, the result has been nail enamels having poor gloss and adhesion.
An object of the present invention is to overcome these disadvantages.
Another object of the invention is to produce hypo-allergenic nail polishes approximating the quality and characteristics of ordinary nail polishes.
Still another object of this invention is to produce a superior nail polish which is hypo-allergenic and can thus be utilized as a universal nail polish.